The use of nickel electroplating baths to obtain a satin finish are generally known. An electroplating bath containing an aqueous nickel solution and fine insoluble inorganic particles, which are suspended in the solution by air agitation, has been used to simultaneously deposit nickel and the fine particles on the material plated. However, in this method some of the suspended particles are inadvertently and separately deposited on the surface of the plated materials and must be removed. This may require an additional manual step with the inherent disadvantage of possibly leaving fingerprints on the plated materials.
Another nickel electroplating bath for obtaining a satin finish is described in U.S. Pat. Nos. 3,839,165 and 3,839,166. The electroplating baths described in the patents include a nonionic, alkylene oxide surfactant which has the following formula R.sub.1 [X(R.sub.2 O).sub.m (R.sub.3 O).sub.n ].sub.p R.sub.4 wherein X is selected from the group consisting of oxygen, sulfur or --NH--, R.sub.1 and R.sub.4 are selected from the group consisting of hydrogen and an organic radical, R.sub.2 and R.sub.3 are selected from the group consisting of ethylene and propylene and m, n and p are whole numbers. The nonionic surface active agents form turbid solutions at 40.degree. to 75.degree. C. Patentees in carrying out the described electroplating method utilize a "cloud point phenomenon" to obtain a satin finish. The nonionic surface active agents though readily soluble at the lower temperatures are difficulty soluble at higher temperatures, at which they rapidly flocculate. Further, the electroplating characteristics of the bath change during periods of use within, for example, less than about 2 hours such that the appearance of the nickel plated surfaces change during the plating operation and are not uniform. A particular problem with using the baths described in the patents is that it is very difficult to obtain a satin finish of uniform grain size. In order to regenerate the baths they should be first cooled and then reheated. Further, the apparatus used to regenerate the baths is relatively expensive.
In still another method for obtaining a satin finish, the surface to be plated is first finely roughed by sandblasting which is costly and substantially adds to the expense of the plating operation.
An object of the present invention is to provide an improved electroplating bath and method for obtaining a uniform satin finish of the metal plate surface on the material plated.
Another object is to provide an improved nickel electroplating emulsion bath and method for obtaining a uniform satin-finish nickel plate surface on the material plated.
Another object is to provide a stable nickel electroplating emulsion bath which during use provides a uniform satin-finish nickel plate surface on the material plated.
Another object of the invention is to provide a stable nickel electroplating emulsion bath which can be used, be allowed to stand for extended periods of time and used again to provide a uniform satin-finish nickel plate surface on the material plated.
A further object of the invention is to provide a stable nickel electroplating emulsion bath which can be regenerated after use easily and inexpensively without the use of special regeneration apparatus.
A still further object is to provide a stable nickel electroplating emulsion bath which efficiently utilizes electrical current in operation of the bath to plate nickel on the surface to be plated.